Could you describe or clarify when you have the pain and what activities cause it? For instance, are you saying that you normally don't have back pain, but had it during this one time of practicing Grasp Sparrow's Tail? Or are you saying that you suffer from chronic pain and that Grasp Sparrow's Tail was particularly challenging? Or are you saying something else?

I was hoping someone else might have an answer to your problem, because I am somewhat mystified. For us, Grasp Sparrow's Tail is merely one of many postures and is probably much less demanding on the back than most. I can't imagine why you would have a problem with this posture and not with others in the form.

I find that doing the form has a short-term neutral effect on my back whenever I am flirting with back pain; however, I believe the long-term effect is good. I find that doing push hands circles has a short-term positive effect, whenever I have had a little back pain.